Electric thruster, a method of stopping an electric engine included in such a thruster, and a satellite including such a thruster

Abstract

An electric thruster includes at least one electric engine, a feed system for the engine including a high-pressure tank of ionizable gas, a low-pressure buffer tank connected to the high-pressure tank by a valve, and a system of pipes for conveying the gas from the low-pressure buffer tank to an anode and to a cathode of the engine. The low-pressure buffer tank is in open connection with the engine. The thruster detects that a magnitude of the discharge current between the anode and the cathode is less than a threshold value and switches off the discharge voltage as a result of the detection. The thruster can be for use in a satellite.

The invention claimed is: 
     
       1. An electric thruster comprising:
 at least one electric engine including an anode, a cathode, and a gas manifold; 
 a feed system for the engine, the feed system comprising: 
 a high-pressure tank of ionizable gas; 
 a low-pressure buffer tank connected to the high-pressure tank by a means for dropping a pressure of the gas; 
 at least one valve configured to open, close, or regulate a flow rate of gas between the high-pressure tank and the low-pressure buffer tank; and 
 a system of pipes for conveying the gas from the low-pressure buffer tank to the gas manifold of the engine; and 
 power electronics configured to deliver or not deliver electric power to the engine by applying or interrupting a discharge voltage between the anode and the cathode; 
 wherein the low-pressure buffer tank is in open connection with the gas manifold and with the anode and with the cathode; and 
 further comprising means for detecting that a magnitude of the discharge current between the anode and the cathode is less than a threshold value and for interrupting the discharge voltage as a result of making the detection. 
 
     
     
       2. An electric thruster according to  claim 1 , wherein the threshold value is about 1 mA for an engine when a nominal value of the magnitude of the discharge current is about 1 A. 
     
     
       3. An electric thruster according to  claim 1 , further comprising a restrictor between the high-pressure tank and the low-pressure buffer tank, and wherein the low-pressure buffer tank has a capacity of less than 20 cm 3 . 
     
     
       4. An electric thruster according to  claim 1 , further comprising a regulator member between the high-pressure tank and the low-pressure buffer tank, together with means for controlling the regulator member so as to obtain at an outlet from the low-pressure buffer tank a pressure that varies in amplitude by less than 5% around a setpoint pressure. 
     
     
       5. An electric thruster according to  claim 4 , wherein a mean value of the pressure is in a range of 0.1 bars to 10 bars. 
     
     
       6. A satellite comprising an electric thruster according to  claim 1 . 
     
     
       7. A method of controlling an electric engine including an anode, a cathode, and a gas manifold, the engine being included in an electric thruster that includes:
 a feed system for the engine, the feed system including:
 a high-pressure tank of ionizable gas; 
 a low-pressure buffer tank connected to the high-pressure tank by means for dropping a pressure of the gas, and in open connection with the engine; 
 at least one valve configured to open, close, or regulate a flow rate of gas between the high-pressure tank and the low-pressure buffer tank; and 
 a system of pipes for conveying the gas from the low-pressure buffer tank to the gas manifold; and 
 power electronics configured to deliver or not deliver electric power to the engine by applying or interrupting a discharge voltage between the anode and the cathode; 
 
 the method comprising, with the low-pressure buffer tank being in open connection with the anode and with the cathode: 
 closing the valve to interrupt the flow of gas between the high-pressure tank and the low-pressure buffer tank; 
 detecting a magnitude of the discharge current between the anode and the cathode that is lower than a threshold value; and 
 switching off the discharge voltage as a result of making the detection.